Microbleed patterns in critical illness and COVID-19

Background: Cerebral microbleeds are increasingly reported in critical ill patients with respiratory failure in need of mechanical ventilation and/or extracorporeal membrane oxygenation (ECMO). Typically, these critical illnessassociated microbleeds involve the juxtacortical white matter and corpus callosum. Recently, this pattern was reported in patients with respiratory failure, suffering from COVID-19. Materials and methods: In this retrospective single-center study, we listed patients from March 11, 2020 to September 2, 2020, with laboratory-confirmed COVID-19, critical illness and cerebral microbleeds. Literature research was conducted through a methodical search on Pubmed databases on critical illness-associated microbleeds and cerebral microbleeds described in patients with COVID-19. Results and discussion: On 279 COVID-19 admissions, two cases of cerebral microbleeds were detected in critical ill patients with respiratory failure due to COVID-19. Based on review of existing literature critical illnessassociated microbleeds tend to predominate in subcortical white matter and corpus callosum. Cerebral microbleeds in patients with COVID-19 tend to follow similar patterns as reported in critical illness-associated microbleeds. Hence, one patient with typical critical illness-associated microbleeds and COVID-19 is reported. However, a new pattern of widespread cortico-juxtacortical microbleeds, predominantly in the anterior vascular territory with relative sparing of deep gray matter, corpus callosum and infratentorial structures is documented in a second case. The possible etiologies of these microbleeds include hypoxia, hemorrhagic diathesis, brain endothelial erythrophagocytosis and/or cytokinopathies. An association with COVID-19 remains to be determined. Conclusion: Further systematic investigation of microbleed patterns in patients with neurological impairment and COVID-19 is necessary.